Hepatocellular cancer (HCC) is the most common primary tumor of the liver. It has an extremely high mortality to incidence ratio (0.93) and is a growing national and existing global health concern. Sorafenib, a multi-targeted kinase inhibitor, is the only FDA approved therapy for patients with advanced/metastatic disease but only results in a median survival of 11.7 months and is poorly tolerated. As such, there is a significant unmet need for novel therapeutic strategies in advanced HCC. Oncolytic virotherapy constitutes an exciting and novel anti-cancer therapeutic strategy that harnesses advances made in the arenas of virology, gene therapy, genomics, molecular biology, immunology and synthetic biology. The proposal entails utilization of multiple extremely high-risk/high-reward strategies involving recombinant vesicular stomatitis viruses in treatment of advanced HCC patients using three disparate but interconnected strategies. The first strategy involves conduct of a first-in-human trial with vesicular stomatitis virus with human interferon beta gene insert (VSV-hIFN-B) in patients with HCC to establish a maximum tolerated dose (MTD), toxicity profile and biodistribution profile for the agent. Preliminary evidence of anti-tumor activity manifest as imaging response (mRECIST) in 4 of 6 treated patients, tumor necrosis (4 of 6) and tumor marker reduction (alpha-fetoprotein decrease in 2 of 4) has been observed thus far. Evaluation of the type I interferon response by serial assessment of transcriptome dynamics (RNA-Seq) in treated patients may ultimately provide an approach to identify tumors with the highest probability of benefit. The second strategy constitutes pursuit of dual oncolytic virotherapy (dual OV) in HCC patients. Dual OV with VSV-hIFN-B and a recombinant vaccinia virus (Pexa-Vec/JX-594) with GM-CSF transgene exploits complementary and synergistic mechanisms of action of VSV-hIFN-B and JX-594 and disparate transgenes (hIFN-B for VSV vs. GM-CSF for JX-594). Additionally, it has been shown pre-clinically that vaccinia suppresses the type I interferon response selectively in proliferating tumor cells, resulting in >1000 fold viral infectin and spread of VSV when used in combination. A pre-clinical toxicology study followed by a Phase IB clinical trial of VSV-hIFN-B + JX-594 in HCC will be conducted to demonstrate proof-of-concept. In a second dual OV approach, MV-NIS, a recombinant measles virus with thyroidal sodium iodide transporter (MV-NIS) will be combined with VSV-hIFN-B in a pre-clinical/toxicology study followed by a Phase IB study in HCC given the disparate mechanism of action of MV-NIS compared to VSV-hIFN-B. Finally, VSV-FH is a fusion construct enabled by synthetic biology that amalgamates the genomes of VSV and the Edmonston strain measles virus (MV). VSV-FH is able to elicit cell kill with both VSV mediated cytotoxicity and MV- mediated syncytial destruction. Additionally, it does not carry the risk of VSV associated encephalitis and unlike VSV does not have broad tropism and is instead targeted to CD46 which is overexpressed in HCC compared to benign liver tissue. The third strategy focuses on toxicological/pre-clinical evaluation of VSV-FH in HCC to allow for eventual clinical translation o VSV-FH in HCC. While the proposed applications of OV are in advanced HCC, demonstration of feasibility and optimization of these approaches has the potential to be applied to a multitude of tumor types.